Applications of uv leds for disinfection

ABSTRACT

A variety of applications for UV LEDs that are integrated into a system are described, where the UV light is used for disinfection of air or surfaces, or used to detect the scattering light by particles, or used for skin treatment. In one embodiment, the UV light from the UV LEDs is generated internal to a housing and is optically coupled to a transparent or translucent surface touched by the human finger, such as a touch screen, a fingerprint scanner, backlit buttons or keys, a toggle of a light switch, a door knob, etc. The UV light is emitted through the touched surface to periodically disinfect the surface. A visual indication of the UV LEDs being energized is provided for safety, such as energizing visible light LEDs or a phosphor on a portion of the touched surface.

FIELD OF INVENTION

The present invention relates to various applications of ultraviolet(UV) light emitting diodes (LEDs) for disinfecting air, water, andsurfaces.

BACKGROUND

Useful UV light for disinfecting air, water, and surfaces is generallyconsidered to be in the range between 400 nm and 100 nm. Such UV maybreak down molecular bonds within DNA, which kills or inactivatesmicroorganisms. The specific bands of UV wavelengths for effectivelykilling various types of organisms have been extensively studies and areknown. For example, the wavelength of about 254 nm has been determinedto be optimal for killing common microorganisms found in water and air,and the wavelength of 293 nm is optimal for killing certain other typesof microorganisms. These optimal wavelengths are in the UVB range (315nm-280 nm) and UVC range (280 nm-100 nm). Such disinfection is typicallycombined with filtration to filter out larger organisms. The UV exposureto perform such disinfection is typically in the range of 2000-8000uW·s/cm².

Currently, by far the most common UV emitters for disinfection aremercury-vapor lamps and xenon lamps. Such lamps emit a very wide rangeof UV wavelengths, and the vast majority of the emitted wavelengths (anassociated power) have no effect on killing microorganisms. Such emittedwavelengths waste energy and can be harmful to humans over long exposureperiods. Such lamps also need a high voltage power supply, which cancreate safety issues. The ideal UV emitter is one that generates a verynarrow range of UV wavelengths, where the peak emitted wavelength isthat which is the most efficient at killing the microorganisms ofinterest. UV LEDs approach such an ideal UV emitter since almost alloptical power is in a very narrow band of wavelengths, and the peakwavelength can be controlled by the materials used in the active layerof the LED.

UV LEDs useful for disinfection are in their infancy, and commerciallyavailable UV LEDs that emit in the UVB and UVC wavelengths emit lowpower (e.g., less than 10 mW), are very inefficient, and are veryexpensive. The present assignee has developed much more powerful UV LEDsin this wavelength range, and a detailed fabrication process for formingsuch UV LEDs is described in U.S. patent application Ser. No.14/635,903, filed Mar. 2, 2015, assigned to the present assignee andincorporated herein by reference.

It is inevitable that the costs of UV LEDs with a selectable and optimalpeak emission within the UVB and UVC range will come down and the powerlevels per UV LED will greatly increase. Therefore, using such UV LEDsinstead of relatively large mercury-vapor or xenon lamps will becomemuch more cost-effective for disinfection.

Thus, novel designs for various disinfection systems using UVB and UVCLEDs are needed that make use of the added flexibility that small LEDsoffer.

SUMMARY

The present disclosure describes various novel uses for UVB and UVC LEDsfor disinfection. By using UV LEDs, versus relatively largemercury-vapor or xenon lamps, the UV wavelength of interest can be moreefficiently coupled to the medium to be disinfected. Additionally, someof the applications described herein use the smaller wavelength of UV todetect smaller particles in an air flow.

Although a sufficient number of commercially available UVB and UVC LEDSmay be used in the embodiments to supply the required UV exposure(e.g., >2000 uW·s/cm²), the assignee's new, more powerful UV LEDs willgreatly reduce the costs needed to implement the present inventions.

Various systems employing UV LEDs described herein include:

UV LEDs for detecting very small unfiltered particles within an airflow;

-   -   Multiple UV LEDs with different peak wavelengths in a single        system for killing different types of organisms and/or for        detecting different types of organisms/compounds based on        absorption;    -   Systems to more effectively couple UV LED light into air or        water, such as using a fiber optic mesh, parallel light guide        blades, or a light guide with holes;    -   UV LEDs coupled to optical fiber for medical applications, such        as for disinfection during micro-surgery;    -   UV LEDs to detect fluorescent nanoparticles in blood;    -   Use of the inherent waveguiding properties of water to direct UV        LED light, such as for disinfecting foods;    -   UV LEDs to disinfect surfaces touched by the public, such as ATM        keys, keyboards, push buttons, light switches, handles,        fingerprint sensor surfaces, touch screen surfaces, etc.    -   UV LEDs integrated into general illumination white light        structures to disinfect air and surfaces in a room;    -   UV LEDs for skin treatment;    -   UV LEDs in a wearable device for generating vitamin D;    -   UV LEDs to determine the coverage of a liquid substance        containing fluorescent particles.

Other applications are described.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a top down view of a portion of an array of UV LEDs.

FIG. 2 is a bisected cross-sectional view of one of the UV LEDs in FIG.1.

FIG. 3A illustrates a particle detection and disinfection system for anair duct.

FIG. 3B is a flowchart describing the use of the system of FIG. 3A.

FIG. 4A illustrates a system that emits a plurality of narrow UVwavelength ranges for detecting particles and disinfecting the air in anair duct.

FIG. 4B is a flowchart describing the use of the system of FIG. 4A.

FIG. 5 illustrates a technique for emitting UV light along a leakyoptical fiber.

FIG. 6 illustrates how the optical fiber of FIG. 5 may form a mesh forcoupling UV light to a medium flowing through the mesh.

FIG. 7 illustrates the preferred location of the mesh relative to an airfilter.

FIG. 8 illustrates an edge-lit light guide with holes to couple UV lightto a medium flowing through the holes.

FIG. 9 illustrates a circuit board having mounted thereon an array of UVLEDs.

FIG. 10 illustrates an edge-lit light guide that is roughened to leakthe UV light.

FIG. 11 illustrates UV-emitting flat panels in an air or water flow fordisinfecting the medium.

FIG. 12 illustrates how the input voltage supply and the power converterfor the UV LEDs may be remotely located.

FIG. 13 illustrates a tool that may be used in microsurgery to disinfectan area inside the patient's body.

FIG. 14 illustrates how UV and visible light may be coupled to aflexible optical fiber to deliver the light to an area inside apatient's body for disinfection and to view the area with a remotecamera.

FIG. 15 illustrates how the UV light may use a stream of water as alight guide to delivery UV light to the surface of food fordisinfection.

FIG. 16 is a cross-sectional view of a light switch with internal UVLEDs for disinfecting a translucent switch lever.

FIG. 17A is a cross-sectional view of a fingerprint sensor using UV LEDsto supply UV light to a scanner surface to disinfect the surface.

FIG. 17B is a flowchart describing the used of the system of FIG. 17A.

FIG. 18A illustrates a display and touch screen system where UV LEDs areused to disinfect the surface of the touch screen.

FIG. 18B is a flowchart describing the use of the system of FIG. 18A.

FIG. 19A illustrates a system for disinfecting push-buttons using UVLEDs.

FIG. 19B is a flowchart describing the use of the system of FIG. 19A.

FIG. 20A illustrates a general lighting system that also includes UVLEDs for disinfecting surfaces and the air.

FIG. 20B is a flowchart describing the use of the system of FIG. 20A.

FIG. 21 illustrates a system for focusing UV light onto skin.

FIG. 22 illustrates a wristband for supplying UV light to the wearer'sskin to generate vitamin D.

FIG. 23A illustrates a bottled liquid containing nanoparticles of aphosphor to visibly determine coverage when the applied liquid isenergized by UV light.

FIG. 23B is a flowchart describing the use of the system of FIG. 23A.Elements that are the same or equivalent are labeled with the samenumerals.

DETAILED DESCRIPTION

Commercially available UVA, UVB, and UVC LEDs may be used in the variousembodiments for disinfection. FIGS. 1 and 2 are examples of theassignee's own UVB and UVC LEDs that may also be used. FIG. 1 is a topdown view of a portion of an array of UV LEDs 12, and FIG. 2 is abisected cross-section of a single UV LED 12. An integraltwo-dimensional array of UV LEDs is not required for the inventions,since individual segmented UV LEDs may also be used. A narrow strip ofUV LEDs may be useful in some of the embodiments. Any number of UV LEDscan be employed in the embodiments depending on the desired opticalpower.

The UV LEDs are typically GaN-based, and commonly AlGaN. The activelayers of the devices described herein may be configured to emit UVA(peak wavelength between 340 and 400 nm), UVB (peak wavelength between290 and 340 nm), or UVC (peak wavelength between 210 and 290 nm)radiation.

The array of UV LEDs 12 is formed on a single substrate 14, such as atransparent sapphire substrate. Other substrates are possible. Althoughthe example shows the UV LEDs 12 being round, they may have any shape,such as square. The light escapes through the transparent substrate, asshown in FIG. 2. The UV LEDs 12 may be flip-chips, where the anode andcathode electrodes face the printed circuit board, or a wire bond may beused for one or both electrodes.

All semiconductor layers are epitaxially grown over the substrate 14. AnAlN or other suitable buffer layer (not shown) is grown, followed by ann-type region 16. The n-type region 16 may include multiple layers ofdifferent compositions, dopant concentrations, and thicknesses. Then-type region 16 may include at least one Al_(a)Ga_(1-a)N film dopedn-type with Si, Ge and/or other suitable n-type dopants. The n-typeregion 16 may have a thickness from about 100 nm to about 10 microns andis grown directly on the buffer layer(s). The doping level of Si in then-type region 16 may range from 1×10¹⁶ cm ⁻³ to 1×10²¹ cm ³. Dependingon the intended emission wavelength, the AlN mole fraction “a” in theformula may vary from 0% for devices emitting at 360 nm to 100% fordevices designed to emit at 200 nm.

An active region 18 is grown over the n-type region 16. The activeregion 18 may be either a single quantum well or multiple quantum wells(MQWs) separated by barrier layers. The quantum well and barrier layerscontain Al_(x)Ga_(1-x)N/Al_(y)Ga_(1-y)N, wherein 0<x<y<1, x representsthe AlN mole fraction of a quantum well layer, and y represents the AlNmole fraction of a barrier layer. The peak wavelength emitted by a UVLED is generally dependent upon the relative content of Al in the AlGaNquantum well active layer, which can be selected by the manufacturer.

A p-type region 22 is grown over the active region 18. Like the n-typeregion 16, the p-type region 22 may include multiple layers of differentcompositions, dopant concentrations, and thicknesses. The p-type region22 includes one or more p-type doped (e.g. Mg-doped) AlGaN layers. TheAlN mole fraction can range from 0 to 100%, and the thickness of thislayer or multilayer can range from about 2 nm to about 100 nm (singlelayer) or to about 500 nm (multilayer). A multilayer used in this regioncan improve lateral conductivity. The Mg doping level may vary from1×10¹⁶ cm ⁻³ to 1×10²¹ cm ³. A Mg-doped GaN contact layer may be grownlast in the p-type region 22. The Mg doping level can vary from 1×10¹⁶cm⁻³ to 1×10²¹ cm⁻³.

The semiconductor structure 15 is etched to form trenches between the UVLEDs 12 that reveal a surface of the n-type region 16. The sidewalls 12a and 12 b of the UV LEDs 12 may be vertical or sloped. The height 38 ofeach UV LED 12 may be between 0.1-5 microns. The widths 31 and 39 at thebottom and top of each UV LED 12 may be at least 5 microns. Otherdimensions may also be used.

Before or after etching the semiconductor structure 15 to form thetrenches, a metal p-contact 24 is deposited and patterned on the top ofeach UV LED 12. The p-contact 24 may include one or more metal layersthat form an ohmic contact, and one or more metal layers that form areflector. One example of a suitable p-contact 24 includes a Ni/Ag/Timulti-layer contact.

An n-contact 28 is deposited and patterned, such that n-contact 28 isdisposed on the substantially flat surface of the n-type region 16between the UV LEDs 12. The n-contact 28 may include a single ormultiple metal layers. The n-contact 28 may include, for example, anohmic n-contact 30 in direct contact with the n-type region 16, and ann-trace metal layer 32 formed over the ohmic n-contact 30. The ohmicn-contact 30 may be, for example, a V/Al/Ti multi-layer contact. Then-trace metal 32 may be, for example, a Ti/Au/Ti multi-layer contact.

The n-contact 28 and the p-contact 24 are electrically isolated by adielectric layer 34. Dielectric layer 34 may be any suitable materialsuch as, for example, one or more oxides of silicon, and/or one or morenitrides of silicon, formed by any suitable method. Dielectric layer 34covers n-contact 28. Openings formed in dielectric layer 34 exposep-contact 24.

A p-trace metal 36 is formed over the top surface of the device, andsubstantially conformally covers the entire top surface. The p-tracemetal 36 electrically connects to the p-contact 24 in the openingsformed in dielectric layer 34. The p-trace metal 36 is electricallyisolated from n-contact 28 by dielectric layer 34.

Robust metal pads terminating the p-trace metal 36 and n-contact 28 areprovided outside of the drawing for connection to power supplyterminals. The array of UV LEDs may be mounted on a support substrate,such as a printed circuit board, which may have an electrical patternfor connection to a power source. Other circuits may also be mounted onthe printed circuit board.

A single UV LED 12 may be made any size to emit a desired optical power.

The remaining figures illustrate various examples of systems that makeuse of the UV LEDs 12 to achieve various functions, such as thedetection of particles (including microorganisms) and the disinfectionof mediums.

Detecting Particles in Air and Disinfecting the Air

FIG. 3A illustrates a system that detects particles in an air flow, orin a sample of air, and optionally disinfects the air to killmicroorganisms. The system may be located in an air duct.

A UV source 40 that contains UVB and/or UVC LEDs directs UV lightthrough an air stream or a static sample of air 42. The air 42 may berestricted in a chamber. The UV source 40 may output a wide emissionusing a two-dimensional array of UV LEDs so that a relatively largevolume of air is analyzed for each sample. Alternately, the UV source 40may generate a narrower beam and sample a smaller volume of air.

The air 42 may be prior to or after being filtered by a suitable porousfilter. It is known to use visible light to determine attenuation byscattering or absorbing particles in air; however, the relatively longwavelengths of such light are not scattered or absorbed by very smallparticles on the order of the UV wavelength. Practical porous filterscan filter out larger sizes of particles but cannot filter out such verysmall particles. The UV light has a wavelength that is much smaller thanthat of visible light, so the light can be scattered and/or absorbed byvery small particles in post-filtered air. Such scattering or absorptionattenuates the UV light that is detected by a photodetector 46 sensitiveto the UV light. The system is controlled by a programmed processor andmemory unit 48. Any other suitable controller may be used in allembodiments, such as a state machine.

The process of FIG. 3B is used to detect particles in the air flow andoptionally disinfect the air.

In step 50, the system is calibrated to establish a baseline, whichrepresents a signal by the photodetector 46 representing 100% clean air.This may be done by testing a closed system in a controlled environment.Such baseline data is stored in the memory.

In step 52, the air to be analyzed is flowed between the UV source 40and the photodetector 46. Alternatively, a portion of an air flow isperiodically captured in a sampling enclosure containing the UV source40 and the photodetector 46. In the example of FIG. 3A, some of the UVlight is scattered by a particle 54, such as dust or a microorganism,and this light is absorbed by the walls of the chamber or by theparticle 54 itself.

In step 56, the amount of UV light that is detected by the photodetector46 over a unit of time is detected and compared to the baseline. Thedifference is the attenuation of UV light due to the light beingscattered or absorbed.

In step 58, the processor correlates the measured attenuation to thenumber of particles (or other characteristic about the particles) perair volume to generate relatable data, such as the percentage ofparticles in the air. The data is periodically output for furtheranalysis.

At the same time, in step 60, the UVB or UVC light kills themicroorganisms in the air. Some microorganisms and compounds fluorescein UV light, and this fluorescence may also be detected by thephotodetector 46 or other detector and presented in the data. Thus,there is synergy in the UV light detecting very small post-filteredparticles and the same UV light killing microorganisms and/or causingfluorescence of the particles.

In step 62, the results are reported and a warning may be activated ifthe data indicates a dangerous level of particles in the air.

UV Source Emitting Multiple Peak Wavelengths for Targeting SpecificMicroorganisms

Research has identified the specific wavelengths that are most effectivein killing certain common microorganisms. These wavelengths aretypically in the range of 240 nm-280 nm, which is in the UVC range. Forexample, the bacteria anthrax is most efficiently killed with awavelength of about 253-254 nm. Other microorganisms are mostefficiently killed with other narrow ranges of wavelengths in the UVCrange.

The prior art uses a very wide band UV emitter, comprising a gas withina vacuum tube energized with a high voltage, to perform such detectionor disinfection. The vast majority of the optical power emitted by sucha wide band emitter is wasted energy. Such a high power of UV light canbe dangerous to humans over a prolonged period.

FIG. 4A illustrates a detection and disinfection system that outputs aplurality of very narrow ranges of UV wavelengths for killing selectedtypes of microorganisms. There is little wasted optical energy since allof the wavelengths are calculated to achieve a specific function.Generally, an energy savings of over 90% can be achieved versus using awide band UV emitter.

In the generally arbitrary example of FIG. 4A, five different types ofUV LEDs 12 are housed in a reflective housing 70 that has a light exitopening for directing the light to a wide band photodetector 72. Thepeak wavelengths of 253 nm and 293 nm are known to be very effective fordisinfection. The medium to be disinfected is shown as air 73, but anyother medium, such as water, can be similarly disinfected. The emittedlight for each wavelength may be a broad beam or a narrow beam. The UVLEDs 12 may be formed in a two-dimensional array, and the number of UVLEDs 12 of each type is determined based on the required optical powerneeded.

Although all the UV LEDS 12 may be energized at once, there is a benefitin sequentially energizing the UV LEDs 12, using the multiplexer 74, toobtain information relating to each peak wavelength. For example, somewavelengths cause a particular type of microorganism to fluoresce, andsuch fluorescence is detected by the photodetector 72. Also, somemicroorganisms absorb only a narrow wavelength of UV light, and suchabsorption (relative to a baseline) can be detected by the photodetector72 in conjunction with the processor and memory unit 76.

FIG. 4B illustrates a method that may be performed by the system of FIG.4A.

In step 80, the optimal UV peak wavelengths for killing or detecting thetarget microorganisms and/or compounds are determined. This can be doneby simply researching existing papers on such optimal wavelengths.

In step 82, the UV LEDs that can emit such peak wavelengths areincorporated into the UV source 70.

In step 84, air or other medium is flowed between the UV source 70 andthe photodetector 72.

In step 86, the different UV LEDs 12 are multiplexed so that thedifferent wavelengths are emitted at different times. If required,certain wavelengths may be emitted for longer times than others. Thephotodetector 72 detects the optical power received for each wavelength.The processor 76 associates the output of the photodetector 72 with thewavelength, which also correlates to the targetedmicroorganism/compound.

In step 88, the processor 76 correlates the attenuation at eachwavelength to the amount of absorption or scattering by the targetedmicroorganism/compound, which can be used to determine the quantity ofthe targeted microorganisms/compounds in the sample. The processor 76may also correlates the fluorescence at each wavelength to the targetedmicroorganism/compound.

In step 90, the emitted UV also kills the targeted microorganisms.

In step 92, the results of the detection are reported. A warning isactivated if appropriate.

Techniques for Coupling UV Light to a Medium

FIGS. 5-11 illustrate techniques to efficiently couple UV lightgenerated by UV LEDs to air, water, or other flowing mediums. Thesetechniques may be used in the systems of FIGS. 3 and 4.

FIG. 5 illustrates a UV source 94 containing UV LEDs. The UV light isemitted through a small opening and coupled to the end of an opticalfiber 96. The fiber 96 is roughened along its length to evenly leak theUV light 98 over a wide angle.

FIG. 6 illustrates multiple fibers 98, each emitting UV light,configured as a mesh 99, with openings to allow the air 100 or water topass through. The mesh 99 can be any size. The configuration enables theair or water to be exposed to UV light from all directions, maximizingthe exposure.

FIG. 7 illustrates how the mesh 99 may be positioned downstream from anair filter 102 so most particles are already removed from the air andonly small particles and microorganisms remain.

FIG. 8 illustrates a thin, edge-lit, light guide 104 having an array ofholes 106 through which air 100 or water flows. The light guide 104 ispositioned in the path of the air or water. The hole sidewalls interceptthe UV light in the light guide 104 and cause UV light to be emitted inthe holes 106. The UV source 94, containing UV LEDs, is coupled to theedge of the light guide 104, which may be a transparent acrylic sheet orother transparent polymer. The light guide 104 surfaces may be roughenedto leak the UV light over its surfaces to further expose the air 100 toUV light.

FIG. 9 illustrates how the UV LEDs 12 can be mounted as an array on acircuit board 108. Air or water is then passed in front of the circuitboard 108 to expose the air/water to the UV light 109.

FIG. 10 illustrates how a light guide 110, such as an acrylic sheet, maybe edge-lit by UV LEDs in the UV source 94, and the surfaces of thelight guide 110 are roughened to leak out the UV light 111. Air or wateris then passed in front of the light guide 110 to expose the air/waterto the UV light. The UV emission may be bidirectional.

FIG. 11 illustrates how the circuit boards 108 or light guides 110(panels) may be positioned in an air/water flow to channel the air/waterfor maximum exposure. By placing a large number of the panels closetogether, the flowing medium is exposed to a high level of UV for anextended time.

Typically, LEDs are driven by a current regulator (a power converter)that receives an unregulated input voltage. FIG. 12 illustrates how theUV source 94, containing any number of UV LEDs, can be connected to apower converter 114 via a flex-cable 116 (or other form of flexibleconductor), where the input voltage Vin may be supplied via wires to thepower converter 114. Since the power converter 114 regulates thecurrent, it should be fairly close to the UV LEDs to limit theresistance of the flex-cable 116. However, the wires conducting Vin maybe long since the power converter 114 will compensate for any voltagedrop along such wires. By using the flex-cable 116, the power converter114 may be located in an optimal location.

Medical Applications of UV LEDS

It is known to use a wide bandwidth germicidal UV lamp during surgery tokill bacteria. However, only a small part of the wavelength is effectivein killing the targeted bacteria, such as a wavelength about 200 nm. Thevast majority of the wavelengths is not performing any useful functionand can be dangerous to the patient. The optimal UV emitter is one thatemits only at the optimal wavelengths, such as around 200 nm, and wherethe UV light is directed only to the area of interest.

In microsurgery, two or three small holes are formed in the patient, andthe operation is carried out using narrow tools entering the patient'sbody through the holes.

FIG. 13 illustrates a disinfection tool 120 for killing bacteria duringmicrosurgery. A UV source 94 contains one or more UV LEDs emitting thewavelengths of interest. The UV source 94 may comprise a reflectivechamber having a small exit window through which all UV light exits. TheUV light is coupled to the end of an optical fiber 122, whose end area124 is roughened to leak out all the UV light 126. The thickness of thefiber 122 may be on the order of 25 microns. The surgeon inserts thefiber 122 into one of the holes in the patient for disinfecting only thearea in which the surgeon is operating using microsurgery. The UV source94 may also contain white light LEDs or other visible-light LED forilluminating the target area within the patient during surgery. Thefiber 112 may be coated with any suitable material for safety. Killingharmful bacteria is particularly important during operations on thestomach, intestines, bladder, kidney, and liver.

FIG. 14 illustrates how a center optical fiber 128 may be used tooptically couple an image received at one end of the fiber 128 to avideo camera 130 at the other end during microsurgery. To provideillumination and disinfection during the surgery, an outer transparentoptical layer 132 is coaxial with the fiber 128. Both UV (e.g., peakwavelength at 200 nm) and visible light from a light source 134 areoptically coupled to one end of the optical layer 132, and this light136 leaks out the opposite end of the optical layer 132 to illuminateand sanitize the surgical area. For example, the small LEDs (less than 1mm in width) may be directly facing the end of the optical layer 132 forcoupling light into the optical layer 132. The tool may be thin (lessthan 0.5 cm) and flexible, allowing it to be inserted into a small holein a patient's body during microsurgery.

Additionally, it may be useful to inject a liquid containingnanoparticles of an inorganic phosphor into the bloodstream and learnabout the patient's body by viewing the locations of the nanoparticlesin the body. The tool of FIG. 14 may be used to energize and observe thephosphor at particular locations. The visible light LEDs may be turnedoff.

Techniques for Directly Coupling UV Light into a Water Stream forDisinfecting a Surface

It is known that certain wavelengths of UV light kill mold and othermicroorganisms that grow on food, and the UV light extends the shelflife of such food. However, constantly exposing the food to the UV lightis not efficient and may impose a danger.

Food is typically washed with water during processing. A contiguousstream of water acts like a light guide. FIG. 15 illustrates asimplified washing system that directly couples the UV light to thesurface of the food for maximum UV exposure. A pipe 140 has atransparent window 142 through which UV light from a UV source 94,containing UV LEDs, is coupled to a stream of water 144. The UV light146 is shown being reflected within the stream of water 144 inside andoutside of the pipe 140. The water “containing” the UV light is used toclean and disinfect the food 146, such as vegetables and fruit, on aconveyor belt 148. Such washing may also be periodically performed whilethe food is being displayed. Other types of water cleaning systems mayalso be used. Even if the stream of water breaks up before contactingthe food, such as with a spraying system, the UV light exiting the pipe140 will still be directed toward the food.

Techniques to Disinfect Touched Surfaces

There are many surfaces that are touched by the public, and germs arespread to others via such touching. Such surfaces include lightswitches, door handles, ATM keypads, keyboards, touch screens,fingerprint readers, elevator buttons, etc. Rather than simply exposingthe touched surfaces to externally-generated UV light, the followingtechniques integrate UV LEDs into such systems.

FIG. 16 illustrates a light switch module 150 having a lever 152 that istoggled to turn on or off a light, represented as a load 154. The switchmodule 150 has terminals that are connected to ground (or neutral) and ahot lead. UV LEDs 156, emitting wavelengths that are optimal for killingthe target microorganisms, are located within the switch module 150 andreceive power by either a separate power supply or the voltagedifference that is present across the switch module terminals when theswitch is off. The UV LEDs are naturally only activated when the switchis off, since the UV LED electrodes are effectively shorted togetherwhen the switch is on. This is good for safety since the UV light shouldnot contact skin. The lever 152 is a translucent plastic and leaks theUV light to disinfect the outside surface of the lever 152.

To visually indicate that the UV LEDs 156 are on, the lever 152 may becoated with a phosphor or a fluorescent material that emits a visiblelight 157 when energized by UV light 158. Thus, the glowing lever 152serves to identify the position of the lever 152 in the dark.

This same technique of employing UV LEDs within a structure to causelight to leak out a touched surface can be applied to many other systemsthat are touched. For example, a translucent door knob system may employpowered UV LEDs within the system to expose the outer surface of thedoor knob to UV light. In such an embodiment, the UV LEDs may be locatedwithin the translucent door knob itself along with a battery so the doorknob can replace a standard metal door knob.

FIG. 17A illustrates a fingerprint scanner 160 that images a user'sfingerprint (on the tip of finger 162) using a digital imager 164. Inprior art fingerprint scanners, such as used in airports for security,all passengers of a plane may touch the same glass surface for imagingand recording their fingerprints. The operator may decide toperiodically sanitize the glass surface by wiping with a towel. However,germs have already been spread to the passengers that have used thefingerprint scanner.

In FIG. 17A, the light from a UV source 166, containing UV LEDs, iscoupled to the edge of a glass plate 168 that is touched when providinga fingerprint. The glass plate 168 acts as a leaky light guide for theUV light for disinfecting the surface after each fingerprint scan.Alternatively, the UV source 166 may be located below the glass plate168 and is emitted through the top surface of the glass plate 168. Theimager 164 senses when a finger 162 has been removed from the glassplate 168, and a processor 170 controls a power supply 172 to energizethe UV LEDs for a time (e.g., 2 seconds) when there is no finger on theglass plate 168.

Since UV light may damage skin, safety precautions may be used. When theUV LEDs are energized, visible light LEDs in the source 166 are alsoenergized and the visible light is coupled to the glass plate 168 (orilluminated below the glass plate 168) so the operator can visually seewhen the UV LEDs are on. Alternatively, no visible light LEDs are used,but a phosphor layer 174 on the glass plate 168 emits visible light whenenergized by UV light and provides the indication that the UV LEDs areenergized. An exposure of the surface of the glass plate 168 for asecond or two may be sufficient to sanitize the glass surface after eachfingerprint scan.

FIG. 17B summarizes the operation of the fingerprint scanner. In step176, the processor 170 detects that no finger is touching the glassplate 168.

In step 178, the UV and visible LEDs (if used) are automatically brieflyturned on to disinfect the glass surface. In step 180, the nextfingerprint scan is performed, and the process repeats.

FIG. 18A illustrates a conventional capacitive touch screen layer 182overlying a liquid crystal display (LCD) screen 184. The LCD screen 184is backlit with a backlight 186. The touch screen detects the XYposition of a fingertip touch, and the XY position is correlated, via aprocessor, to a function to be performed. The touch screen layer 182 istransparent and may be a glass or plastic plate supporting the XYsensors (e.g., semi-transparent conductor areas). A UV source 188,containing UV LEDs emitting optimal wavelengths for killing targetmicroorganisms, emits UV light that is optically coupled to the edge ofthe touch screen layer 182. The touch screen layer 182 is typicallytranslucent enough (due to the semi-transparent conductors) to act as aleaky light guide to expose the surface to the UV light. The surface maybe roughened to increase the light emission. The UV LEDs are onlyenergized when no touching is sensed or during pre-determined times.

A timer 190 controls the exposure time, and a processor 192 controls thesystem.

Visible LEDs may also be included in the source 188 and are energizedalong with the UV LEDs as a visual indicator that the UV LEDs are on.

FIG. 18B summarizes the operation of the touch screen disinfector. Instep 194, the user sets the timing for the disinfecting, such as at aparticular time of the evening, or after every 10 minutes, etc. Thedisinfecting may also be automatically performed after each touch.

In step 196, the UV and visible LEDs (if any) are energized and, in step198, the UV light impinges on the surface of the leaky touch screen 182to disinfect the surface.

FIG. 19A illustrates a system having translucent buttons 200, such as inan elevator or a keyboard/keypad, where the UV light from a UV source202, containing UV LEDs, is coupled to the edge of a backlight 204 alongwith visible light, such as from white light LEDs in the source 202. Thebacklight 204 is leaky to emit all light in the direction of thetranslucent buttons 200. Pushing a button 200 is sensed by a processor206 for carrying out the desired function. A timer 208 turns on the UVLEDs in the source 202 for a brief period, such as after each buttonpress, to sanitize the buttons 200, whereby the outer surface of thebuttons 200 is exposed to the UV light. The visible LEDs may beconstantly on for the backlight 204.

In another embodiment, the backlight comprises a support surface, andthe visible LEDs and UV LEDs are distributed over the support surfacefor directly illuminating the back of the buttons 200.

FIG. 19B summarizes the operation of the disinfection system of FIG.19A. In step 210, the operator sets the desired timing of the UV LEDsfor disinfection, such as at a certain time, or every 10 minutes, orafter each button press.

In step 212, the white light LEDs are continually energized forbacklighting the transparent buttons 200.

In step 214, the UV LEDs are periodically energized to disinfect thebuttons 200.

General Lighting System Having Integrated UV LEDS for Disinfecting Airand Surfaces

In public places, such as schoolrooms, hospitals, buses, stations,offices, etc., both the air and touched surfaces are ideally sanitizedperiodically to kill microorganisms. FIG. 20A is an intelligent generallighting system using both visible light LEDs and UV LEDs to providegeneral illumination along with disinfection.

A luminaire 220 of any design is typically supported by the ceiling of aroom. The luminaire 220 contains white light LEDs 222 or red, green, andblue LEDs for creating white light. These LEDs 222 may be controlled bya color/brightness controller 224 for illuminating the room with whitelight 226. Since UV light may be dangerous with prolonged exposure, theUV LEDs 228 are only energized when there is no person in the room. Thismay be detected by a motion or heat sensor 230. The UV wavelengths areselected to be optimal for killing the target microorganisms on surfacesand in the air. The UV light 232 may be emitted toward the ceiling anddownward. The upward UV light may be emitted constantly if there is nodangerous downward reflection of the UV light.

FIG. 20B summarizes the operation of the disinfection system of FIG.20A. In step 234, the UV LEDs are turned off when there are peopledetected being in the room and, in step 236, the UV LEDs are turned onwhen the room is empty to disinfect the air and surfaces and removeodors cause by microorganisms.

UV LEDS Used for Skin Treatment

UV light of particular wavelengths is known to mitigate various skinconditions and generate vitamin D.

FIG. 21 illustrates a tool 238 used by dermatologists that focuses UVlight only on the small skin area 240 to be treated. In this way, thereis no damage to other areas. The tool 238 includes a handle 242, UV LEDsand visible light LEDs in a source 244, and an optional lens 246 forfocusing the light. The visible light LEDs are energized along with theUV LEDs to illuminate the skin surface while also indicating that the UVLEDs are energized.

FIG. 22 illustrates a resilient wristband 250 worn on the wrist orankle. The outer surface may be opaque and have a reflective innersurface. One or more UV LEDs 252, emitting optimal wavelengths forgenerating vitamin D, are integrated into the wristband 250 to couplethe UV light into a transparent or translucent inner layer 254 of thewristband 250. Alternatively, the UV LEDs may be distributed around thewristband 250. A battery power source and any controller are integratedwith the UV LEDs within the layer 250. A low power, but long, exposureof the skin to the UV light safely creates vitamin D in the bloodstream, which is carried to other parts of the body. Wearing thewristband 250 on the wrist is optimal due to the proximity of majorarteries and large veins to the skin surface. The battery may berecharged using inductive coupling. An on/off switch may be provided ora sensor automatically determines that the wristband 250 is being worn.

FIG. 23A illustrates a bottle of skin lotion 256, such as for treatmentof a skin ailment or a sun screen. The lotion 256 contains inertnanoparticles of a phosphor or fluorescent material that are uniformlysuspended in the lotion 256. The proper coverage of the lotion 256 on aperson's skin is verified by illuminating the treated area with UV lightfrom a UV source 258 containing UV LEDs. The nanoparticles in theapplied lotion will provide a visual indication of the location of thelotion 256 on the body.

The invention also applies to suspending phosphor nanoparticles in anyliquid that is to be spread on a surface, including clear varnishes,waterproofing treatments, etc.

The operation of the system of FIG. 23A is summarized in FIG. 23B. Instep 260, the liquid containing the nanoparticles (e.g., lotion 256) isspread on a surface, such as skin. In step 262, the UV LEDs areenergized and the UV light is directed to the surface to cause thenanoparticles to emit visible light for detecting the proper coverage onthe surface.

In all cases, although UV LEDs emit a narrow band of wavelengths with apeak wavelength, it may be desired to further narrow the bandwidth. Thismay be done with a multi-layer Bragg filter or other type of opticalfilter.

Many variations of the above-described techniques of FIGS. 3-23 areenvisioned, and the techniques would be customized for each particularapplication. Elements from the various embodiments may be combined asneeded for a particular application.

While particular embodiments of the present invention have been shownand described, it will be obvious to those skilled in the art thatchanges and modifications may be made without departing from thisinvention in its broader aspects and, therefore, the appended claims areto encompass within their scope all such changes and modifications asfall within the true spirit and scope of this invention.

What is claimed is:
 1. A system containing an integral disinfectionapparatus comprising: a first article having a transparent ortranslucent surface that is touched by a human finger; one or more lightemitting diodes (LEDs) emitting ultraviolet (UV) light in the range ofUVB or UVC; a housing supporting the first article and containing theLEDs, wherein the UV light from the LEDs is optically coupled frominside the housing to an outer surface of the first article to at leastpartially disinfect the surface of the first article that is touched bythe human finger; and a timing circuit for automatically controlling theLEDs to be intermittently energized.
 2. The system of claim 1 furthercomprising a visible light emitter within the housing that emits visiblelight only when the LEDs emit the UV light.
 3. The system of claim 1wherein the UV light from the LEDs is optically coupled to an edge ofthe first article, and the first article acts as a light guide to guidethe UV light to the surface that is touched by the human finger.
 4. Thesystem of claim 3 wherein the first article is a touch screen layer overa display device.
 5. The system of claim 3 wherein the system is afingerprint detector having an imager that detects a fingerprint of thehuman finger while touching the first article.
 6. The system of claim 1wherein the first article comprises backlit buttons or keys touched bythe human finger, the system further comprising: a backlight for thebuttons or keys, wherein the light from the backlight includes bothvisible light and the UV light.
 7. The system of claim 6 wherein the UVlight from the LEDs is optically coupled to an edge of the backlight,and the backlight acts as a leaky light guide.
 8. The system of claim 1wherein the LEDs emitting UV light are UV LEDs, the system furthercomprising one or more visible light LEDs, wherein the UV light from theUV LEDs and the visible light from the visible light LEDs are bothoptically coupled to the first article.
 9. The system of claim 8 whereinthe visible light LEDs are only energized when the UV LEDs areenergized.
 10. The system of claim 8 wherein the visible light LEDs areenergized even when the UV LEDs are not energized.
 11. The system ofclaim 1 further comprising a material that emits visible light whenenergized by the UV light to visually indicate that the LEDs areenergized.
 12. The system of claim 11 wherein the material is a phosphordeposited on the first article.
 13. The system of claim 1 wherein thefirst article is a toggle of a light switch module.
 14. The system ofclaim 13 wherein a material on the surface of the toggle emits visiblelight when energized by the UV light to visually indicate that the LEDsare energized.
 15. The system of claim 1 further comprising a controllerthat detects when the first article is not being touched by the humanfinger, wherein the controller controls the timer to energize the LEDswhen the controller detects that the first article is not being touched.16. The system of claim 1 wherein the first article is a door knobhousing the LEDs.
 17. A method of automatically and periodicallydisinfecting a transparent or translucent surface of a first articlethat is touched by a human finger, the method comprising: providing oneor more light emitting diodes (LEDs) emitting ultraviolet (UV) light inthe range of UVB or UVC in a housing, where the housing also supportsthe first article; controlling a timing circuit to automaticallyenergize the LEDs when it is determined that the first article is notbeing touched by the human finger; and optically coupling the UV lightfrom the LEDs from inside the housing to an outer surface of the firstarticle to at least partially disinfect the surface of the first articlethat is touched by the human finger.
 18. The method of claim 17 furthercomprising providing a visual indication that the LEDs are energized.19. The method of claim 17 wherein the step of providing a visualindication that the LEDs are energized comprises energizing one or morevisible light LEDs along with the LEDs that emit the UV light.
 20. Themethod of claim 17 wherein the step of providing a visual indicationthat the LEDs are energized comprises energizing a phosphor that isdeposited on the first article.